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C. J. KLEIN. ATTACHMENT PLUG. APPLICATION FILED AUG.5.1915- Patented Aug. 12, 1919.

. r Amen once.

CHARLES J. KLEIN, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO THE CUTLER-HAMMER MFG. 00., OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

ATTACHMENT-PLUG.

Specification of Letters Patent.

Patented Aug. 12, 1919..

To all whom it may concern:

Be it known that 1, CHARLES J. KLEIN, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and plug wherein the contacts of the base are inaccessible except through narrow slots.

Another object is to provide" a plug of the aforesaid character wherein the cap thereof is provided with a central knot recess and with its contacts so disposed as to render, said recess unobstructed and readlly accessible.

Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates one embodiment of the invention and the same will now be described it being understood that the invention is susceptible of other embodiments falling within the scope of the appended claims;

In the drawing,

Figure 1 is a longitudinal sectional view through the plug;

Fig, 2 is a top plan view of the base or plug member;

Fig. 3 is a longitudinal sectional view through the cap taken at right angles to Fig. 1; and,- I v Fig. 4 is 'a bottom plan view of the cap. Referring more specifically to the drawing, the same shows a base 1 having a screw shell 2 and center terminal 3 for insertion in a standard lamp socket and a detachable cap a having a swivelconnec'tion with the base 1.

The basal, which is of suitable insulating material, is cylindrical'in form and is provided with a lower end disk '5 to clamp an inturned rim 6 of the threaded shell 2 to said base. The opposite end of the base is extended insulating parts.

centrally recessed to receive an annular contact 7, shown as cup-shaped, which in turn receives a cylindrical insulating block 8. All of the aforesaid parts are secured in assembled relation by the center contact screw. The contact 7 constitutes a center contact while the upper extremity of the screw shell 2 provides an outer annular contact 9 concentric with the former contact. The contact portion 9 of the screw shell is surrounded by an insulating collar 10 which in practice may be molded thereon or otherwise fixed thereto to serve as a gripping member for inserting the plug in a lamp socket and also for external insulation of the contact portion 9. Both contacts 7 and 9, as shown, are curved to provide concave grlpping surfaces and both are closely walled in by the several insulating parts. Moreover, the insulating parts are extended slightly beyond the extremities of the contacts and the extremities of the contacts are set into their surrounding insulating walls whereby only their inner faces are accessible and then only after entrance between the Thus the cap receiving end of the plug part appears as a block of insulation with restricted concentric slots and presents a-very neat appearance while it very effectually insures against accidental engagement with the contacts.

The cap is provided with'the usual central conductor opening 11 and with a knot receiving recess 12 adjacent thereto. Also, the cap is provided with the usual annular rim 13 and adjacent to said rim and at-diametrically opposite points with terminal plates 15 and 16 having binding screws 17. The terminal plates, as best illustrated in Fig. 3, are are shaped and arranged concentrically with the conductor opening while being spaced from one another. Terminal plate 15 is provided with perpendicularly and oppositely disposed. contact lugs 18 and 19 and terminal plate 16 is provided With similar contact lugs 20 and 21, each of said lugs being are shaped in cross section and longitudinally split to form a plurality of resilient fingers. The contact lugs are concentrically arranged with respect to the axis .of the plug thereby giving free access to the knot recess and are so disposed as to register with the annular slots in the base for insertion therein. Further, the contact lugs or fingers of each terminal plate are normally spread so as to be slightly contracted When forced into the slots in the base and are provided with bulged extremities to spread after insertion into the slots for engagement with the concave contacts of the base.

It willthus be apparent that the'cap may be readily wired and knotted, and then plugged into the base by a straight push as with the ordinary separable plug but that engagement of the cooperating contacts will not be effected until after an appreclab-le 1nsertion of the cap contacts. Also, it will be apparent that due to the annular formation and concentric arrangement of the base contacts and the similar arrangement of the cap contacts, the cap after belng plugged into the base may be freely rotated with respect thereto while maintaining firm electrical engagement therewith. Still further, it will be apparent that with the arrangement of contacts shown said contacts will interlock ing a releasable connection therebetween and contiguous to the line of division between the cap and the base and that the contacts of .the cap'will yield in all directions radially of the axis of the plug whereby the cap may be readily detached either by straight pull or by leverage at any angle circumferentially of the plug. 'On the other hand, the contacts while readily separable are so constructed as to provide a relatively large contact area and by virtue of the resiliency and opposed relation of the cap contacts to firmly engage throughout such contact area.

What I claim as new and desire to secure by Letters Patent is:

1. A separable attachment plug comprising a plug part and acap, said parts being' provided with cooperating contacts providcertain of said contacts being annular and concentrically arranged to render said connection of a swivel type, said plug part having its contacts terminating in substantially the same transverse plane and having its ca receiving end closed except for restricte openings to receive the cap contacts.

, 2; A separableattachment lug comprising a plug art and a cap, said parts having cooperating contacts providing a swivel and releasa'ble connection therebetween the contacts of said cap projecting substantially equal distances therefrom and said plug part having its cap receiving end closed except for restricted openmgsto receive the cap contacts and also havlng its contacts adjacent to the surface of its cap receiving end.

3. A separable attachment plug comprising a plug part and a cap, said parts having cooperating contacts providing a swivel and releasable connection therebetween, said plug part having its cap receiving end closed except for restricted openings to receive the cap contacts and having its contacts arranged in close proximity to the surface of its cap receiving end and the contacts of said cap being of substantially uniform length and resilient for permitting separation of said cap from said plug part either by leverage or by straight pull.

4. A separable attachment plug including a plug part provided with concentric annular contacts and a cap therefor having a' plurality of sets of normally spread contact lugs to be pluggedwithin each of said annular contacts.

5. A separable attachment plug including a plug part provided with concentric annular contacts and continuous insulating walls exteriorly and interiorly of said contacts and a cap for said plug part provided with contacts to plug into engagement with said annularcontacts through the slots provided by said insulating walls;

6. A separable attachment plug comprising a plug part, a one-piece centrally recessed cap therefor and plugging contacts for said parts providing a swivel connection therebetween, said cap-having its contacts fixed thereto and arranged. in non-obstructive relation with respect to the central opening therein and said ca contacts having binding posts adjacent to said cap opening.

7. A separable attachment plug comprising a plug part having contacts at varying distances from its central axis and a centrally recessed one-piece ca having cooperating plugging contacts 'xed thereto arranged in a non-obstructive relation with respect to the central, opening of said cap and provided with readily accessible ing posts adjacent to said opening.

'8. A one-piece cap for separable attachment plugs'provided with a. central ,conductor opening and knot recess and further provided with contact plug fixed thereto plates being adjacent to said conductor opening and said contact extensions being arranged at different distances from the central axis of said cap and in a non-ob structive relation with respect to said hot recess and said terminal plates.

. 10. A plug part for separable attachment plugs provided with an insulating end having concentric annular slots therein of restricted width and inclosed concentric anb-indnular contacts accessible only through said annular slots. I

11. A plug part for separabie attach- [ment plugs provided with concentric an- .annular slots therebetween to give access to said contacts but said tively narrow.

slots being rela- 12. A plug part for separable attachment plugs provided with concentric an nular contacts and cylindrical insulating walls within and without each contact to restrict the'accessibility thereof, said walls projecting beyond the extremities of said contact.

18. A plug part for separable attach ment plugs provided with concentric annular contacts and cylindrical insulating walls Within and without each contact to restrict the accessibility thereof, said walls projecting beyond the extremities of said contact and each of said contacts having a portion ofl'set from the slot between its respective insulatingwalls.

14. A plug part for separable attachment plugs provided with 'a'screw shell, a center contact at its" plugging end and at its opposite end with contacts for a'cap part, one of said latter contacts comprising the end of said shell and the other being electrically connected with said center contact and insulating walls within and without each of said latter contacts.

15. A plug part for separable attach- "'ment1 plugs lncluding a base provided at oppositeends with electrically connected contacts'and with an external threaded shell serving as a side contact for the plugging-end of said part and also as a second contact for the cap receiving end of said part and an insulating plug clamped within both contacts at the cap receiving end of said plug part.

16. A plug part for separable attach- I ment plugs including a base, a center contact for the plugging end thereof, an

- electrically connected annular contact provided t the cap end Qffifiid base, a threaded shell inclosingsaid base and providing a secondannular contact for the cap end of said base and an insulating plug secured within said first mentioned annular contact.

17 A plug part for separable attachment plugs provided with a base recessed at one end, a cup-shaped contact arranged Within said recess, an insulating; block within said cup-shaped contact, a center contact rod for, the opposite endof, said base providingv means for securing all of said. parts, together, a threaded shell sur-- rounding said base and forming a' second annular end contact concentric with said cup-shaped contact and an insulating collar fixed to said end'of said shell.

CHARLES J. KLEIN. 

